Nigerian soldiers have arrested eight people working for companies contracted by Royal Dutch Shell , military authorities said, following a pipeline fire that the company blamed on damage caused by oil thieves.

Shell's Nigerian unit, Shell Petroleum Development Co. of Nigeria Ltd. (SPDC), shut the 150,000 barrel per day (bpd) Trans Niger pipeline last week after an explosion and a fire in Bodo West, in Ogoniland, an area already heavily polluted by oil spills.

"Troops ... have arrested eight persons in connection with the recent fire outbreak on an SPDC pipeline," Military Joint Task Force (JTF) Spokesman Onyema Nwachukwu said on Monday.

"They will be handed over to an appropriate prosecuting agency if found culpable at the end of the investigations."

Shell said in a statement that it was aware of the arrests and would "cooperate with the investigations".

The company has been pushing the government to make greater efforts to combat stealing of oil - known locally as bunkering - which it blames for the theft of an estimated 150,000 bpd across the industry in Nigeria and for repeated oil spills and fires.

The JTF said the eight people were found on tug boats near the pipeline and that the suspects told them they worked for Steve Integrated Technical Service and Sege Marine, companies that were hired by SPDC to fix broken pipelines.

"They are not bunkerers," a manager at Steve Integrated told Reuters, asking not to be named.

"There was no sign of stolen crude oil on the tug boat as they were only working on repairs. We will continue to work with the JTF," he added.

Sege Marine could not be contacted for comment.

Nigeria's accountant general said last week that oil theft and pipeline vandalism were responsible for a 5 percent fall in monthly government revenues in May.

(Reporting by Tife Owolabi; Additional reporting and writing by Joe Brock)